The energy-loss near-edge structure (ELNES) at the oxygen K edge in two AB2O4 spinels (A=Mg, B=Al,Cr) is reported. In MgAl2O4 the experimental data is successfully modelled within the LDA framework. In the case of MgCr2O4 spin-polarisation, in the form of antiferromagnetic ordering on the Cr sub-lattice, must be included despite the fact that the measurements were performed at approximately 30 ...

Motivated by numerical evidence of the valence-bond ground state of the two-dimensional Heisenberg pyrochlore lattice, we argue using a t-J model that it evolves under doping into novel phases characterized by superconductivity coexisting with the underlying valence-bond solid order. A fermionic mean-field theory supplemented by exact diagonalization results provide strong arguments in favor of...

Lacunar spinels with a chemical formula of $AM_4X_8$ form populous family narrow-gap semiconductors, which offer fertile ground to explore correlation and quantum phenomena, including transition between Mott spin-orbit insulator states, ferro/antiferroelectricity driven by cluster Jahn-Teller effect, magnetoelectric response magnetic skyrmions polar dressing. The electronic properties lacunar a...

We demonstrate that extensive electrochemical shock–electrochemical cycling induced fracture–occurs due to coherency stresses arising from first order cubic-to-cubic phase transformations in the spinels LiMn2O4 and LiMn1.5Ni0.5O4. Electrochemical shock occurs despite the isotropy of the shape changes in these materials. This electrochemical shock mechanism is strongly sensitive to particle size...

Calculations are performed on the free energies for proton-promoted reactions of the lithium-ionbattery electrode material LiMn2O4 spinel in acid, as a function of lithium excess and lithium deficiency relative to stoichiometry. In particular, we consider the dissolution reaction proposed by Hunter (J. Solid State Chem., 1981, 39, 142), in which protons react with lithium manganate spinel to fo...

Materials with the spinel crystal structure exhibit a diverse range of ground states and properties. These result from the interplay of spin, charge and orbital degrees of freedom over the geometrically frustrated pyrochlore sublattice. In certain spinels the interaction of ordered orbitals induces a structural distortion, due to the formation of clusters of directly bonded atoms called orbital...